Ms Martens (32) is alleged to have made the admission to her sister-in-law in the hours after her husband, Jason Corbett (39), died from head injuries at their home in North Carolina.

Details of the alleged admission were outlined by the deceased's sister Tracey Lynch in court last August, but could not be reported until now.

In a separate legal submission, Mrs Lynch also claimed Ms Martens had told a family friend she "wanted to leave Jason because she did not love him any more and did not care what happened to him".

However, Ms Martens is alleged to have decided against this because she would have no right to his children.

The allegations were aired at a behind-closed-doors hearing to decide on the guardianship of Mr Corbett's two children.

Details of the alleged admission can now be disclosed after a transcript was made public by the Davidson County Superior Court. At the hearing, Mrs Lynch and her husband David successfully applied for guardianship of the children, Jack (11) and Sarah (9).

Mrs Lynch argued under questioning that the children needed protection from their stepmother, Ms Martens, who, she said, had admitted to killing her brother. "I spoke to Molly after the event, and her mother. Molly indicated she killed my brother," Mrs Lynch testified.

Ms Martens and her father, former FBI agent Thomas Martens (65), have been charged with second-degree murder and voluntary manslaughter.